Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

It's easy for me to imagine that if we brake the front wheel then there is a chance that I'll flip.

On the other hand if I brake the back wheel, there is no way it'll happen no matter how fast I brake.

But whether I brake the front wheel or back wheel, the force I've added is a backward force at the bottom of the wheel.

So why the different outcome?

share|improve this question
    
One force goes "inward", the other "outward" from the CoG. –  Ignacio Vazquez-Abrams May 28 '12 at 5:24
    
Hmm... it's hard to express this without pictures. I am sure you can imagine right? Or perhaps the break at the back wheel only applies when the backwheel touch the ground. –  Jim Thio May 28 '12 at 8:32

1 Answer 1

up vote 3 down vote accepted

The torque is in the same direction in either case, so the torque wants to lift the back-wheel and flip you over the front whichever wheel you brake with, but when the braking is on the back-wheel, if you lift the back-wheel, the braking force goes away, so the torque goes away. This means that a brake applied to the back-wheel will never be enough (unless it is applied extremely suddenly) to flip the bike, it will just lift the back wheel and reduce the braking to zero, or else make a bouncing back-wheel.

share|improve this answer
    
This is what I suspected. However, as you said your self, what about if the break is so sudden? I feel as if there is something more to this. Anyway, +1 definitely. –  Jim Thio May 28 '12 at 8:33

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.